Antibiotics and light responses in superfused bovine retina

1. Our objective was to study effects of clindamycin and ciprofloxacin on t he electroretinogram (ERG) of isolated bovine retinas. 2. Electroretinograms of isolated superfused bovine retinas were recorded u nder normal conditions and during application of clindamycin and ciprofloxa cin. The b-wave reduction was plotted against the drug concentration. In se veral cases retinal oxygen uptake was also measured. Clindamycin was availa ble only in a preparation containing benzyl alcohol. To differentiate betwe en effects caused by the antibiotic and the alcohol, ERGs were also recorde d under superfusion with benzyl alcohol. To record drug effects on photorec eptors synaptic transmission was blocked using 1 mM aspartate. 3. At concentrations between 0.3 and 10 mM clindamycin significantly reduce d the amplitude of the b-wave of the ERG. A comparable reduction of retinal oxygen uptake was found at concentrations 10-fold higher. Clindamycin, 3 m M, did not affect the a-wave after preincubation with aspartate. Benzyl alc ohol at concentrations of 0.3 and 1 mM did not affect the b-wave, whereas a t higher concentrations the b-wave was found to be reduced. Considerable b- wave reductions were found with ciprofloxacin at concentrations of between 0.03 and 0.6 mM. All effects proved to be fully reversible and dose-depende nt. 4. Ciprofloxacin and clindamycin did both alter neural function in the isol ated superfused bovine retina. The nontoxic dosages found here differ consi derably from results in rabbits after intravitreal injections. This is prob ably due to species differences.